This invention relates to an exhaust bypassing system for a turbocharger. More particularly, it relates to an exhaust bypassing system for a turbocharger suitable for use with an internal combustion engine such as an automobile engine.
An exhaust bypassing turbocharger wherein part of the exhaust gas of an automobile engine is bypassed without passing it through a turbine to regulate the output of the turbine and to control the quantity of air which is compressively fed to the engine by a compressor interlocking with the turbine, has been known from U.S. Pat. No. 3,035,408.
The exhaust bypassing system of the turbocharger of this type is provided with a control valve for regulating the quantity of the exhaust to be bypassed. The control valve has a valve body which opens and closes an exhaust bypass passage, and a rod whose one end has the valve body mounted thereon. The rod extends across an exhaust passage, and a diaphragm is mounted on the end of the rod remote from the valve body. The diaphragm separates a suction pressure chamber which communicates with the outlet portion of the compressor through a suction pressure pipe and an atmospheric pressure chamber which is open into the atmospheric air. A compression spring which holds the diaphragm in pressed contact is disposed in the atmospheric pressure chamber in a manner to surround the outer periphery of the rod. The rod which is attached to the diaphragm is moved by the outlet pressure of the compressor or the exhaust pressure of the engine, to open or close the exhaust bypass passage. A rod guide portion which supports the rod by permitting it to penetrate therethrough is provided in the wall of the engine exhaust passage.
In the exhaust bypassing system of the turbocharger as described above, the control valve is influenced by the exhaust pressure of the engine, and hence, the quantity of the bypass exhaust is not always held in a state proportional to the outlet pressure of the compressor, so that the inlet pressure of the turbine is unreliable. Accordingly, the quantity of the feed air to the engine does not agree with the quantity which the engine requires, and the optimum air fuel ratio is not attained.
In the prior-art exhaust bypassing system for the turbocharger, carbon and corrosive particles which are contained in the exhaust adhere to the rod guide portion, and the operation of the control valve becomes unsmooth. In extreme cases, the carbon etc. stick fast to the guide portion, and the control valve becomes unadjustable.